Optical activity measurements with frequency modulation

Abstract

A system ( 1 ) for measuring the optical activity of a sample ( 2 ) comprises at least one frequency modulation device ( 3 ), at least one synchronization device ( 4 ), and at least one detection device ( 5 ). The frequency modulation device ( 3 ) is configured to modulate a frequency of incident electromagnetic radiation being emitted from a sample ( 2 ) and/or being irradiated on to a sample ( 2 ) with at least one frequency modulation signal (Sf). The synchronization device ( 4 ) is configured to receive the at least one frequency modulation signal (Sf) and to emit at least one detection modulation signal (Sd) being synchronized with the at least one frequency modulation signal (Sf). The system ( 1 ) is configured such that the detection device ( 5 ) detects the electromagnetic radiation (EMs) in synchronization with the detection modulation signal (Sd).

The invention claimed is: 
     
       1. A system for measuring the optical activity of a sample comprising:
 at least one frequency modulation device; 
 at least one synchronization device; and 
 at least one detection device,
 wherein the at least one frequency modulation device is configured to modulate a frequency of incident electromagnetic radiation being at least one of i) emitted from a sample or ii) irradiated on to a sample with at least one frequency modulation signal, 
 wherein the at least one synchronization device is configured to receive the at least one frequency modulation signal, 
 wherein the at least one synchronization device is further configured to emit at least one detection modulation signal being synchronized with the at least one frequency modulation signal, 
 wherein the system is configured such that the at least one detection device detects incident electromagnetic radiation in synchronization with the at least one detection modulation signal, 
 wherein the frequency modulation device is configured to separate components of incident electromagnetic radiation having two or more polarization states into components of electromagnetic radiation having one or more frequencies, and 
 wherein:
 i) the system further comprises at least one masking device, wherein the masking device is configured to mask one or more areas of the detection device such, that the detection device is prevented from detecting incident electromagnetic radiation in these one or more masked areas, wherein the synchronization device is in connection with the masking device, wherein the synchronization device is configured to send the detection modulation signal to the masking device, and wherein the masking device is configured to mask one or more areas of the detection device in synchronization with the detection modulation signal, or 
 ii) the synchronization device is in connection with the detection device, wherein the synchronization device is configured to send the detection modulation signal to the detection device, and wherein the detection device is configured to detect incident electromagnetic radiation in synchronization with the detection modulation signal. 
 
 
 
     
     
       2. The system according to  claim 1 , wherein the system is configured such, that the components of electromagnetic radiation having one or more frequencies are detected simultaneously or temporarily delayed with respect to one another by the detection device. 
     
     
       3. The system according to  claim 1 , further comprising at least one intensity modulation device, wherein the intensity modulation device is configured such, that an intensity of incident electromagnetic radiation is modulated, whereby intensity-modulated electromagnetic radiation is generated. 
     
     
       4. The system according to  claim 3 , wherein the intensity modulation device is at least one of a polarizer or a linear polarizer. 
     
     
       5. The system according to  claim 1 , wherein the detection device is an image sensor and wherein the areas are at least two pixels, and wherein the masking device is configured to mask one pixel at a time. 
     
     
       6. The system according to  claim 5 , wherein the synchronization device is configured such, that a particular polarization state is detected by a particular pixel at a time. 
     
     
       7. The system according to  claim 6 , wherein the synchronization device is configured such, that a particular polarization state is detected by a particular pixel row at a time. 
     
     
       8. The system according to  claim 5 , wherein the areas are at least two pixel rows and wherein the masking device is configured to mask one or more pixel rows at a time, or
 wherein the areas are at least four or exactly four pixel rows and wherein the masking device is configured to mask at least three pixel rows or exactly three pixels rows at a time. 
 
     
     
       9. The system according to  claim 1 , further comprising at least one separating device, wherein the separating device is configured to spatially separate one or more wavelengths constituting incident electromagnetic radiation onto the detection device. 
     
     
       10. The system according to  claim 9 , wherein the separating device is configured to spatially separate one or more wavelengths constituting incident intensity-modulated electromagnetic radiation onto the detection device. 
     
     
       11. The system according to  claim 1 , further comprising an excitation source, wherein the excitation source is configured to excite the sample. 
     
     
       12. The system according to  claim 11 , wherein the excitation source is a laser. 
     
     
       13. The system according to  claim 1 , further comprising at least one of:
 a) one or more polarization conditioning elements, the polarization conditioning elements being configured to change a polarization state of electromagnetic radiation being incident on the polarization conditioning elements, or 
 b) at least one filter element, preferably a Rayleigh filter, which is configured to filter one or more wavelengths of electromagnetic radiation being incident on the filter element. 
 
     
     
       14. The system according to  claim 13 , wherein at least one of:
 a) the polarization conditioning elements are arranged such, that at least one of i) the sample can be irradiated with electromagnetic radiation being unpolarised or ii) noise is reduced, or 
 b) the filter element is at least one of i) a Rayleigh filter or ii) configured to filter one or more wavelengths of intensity-modulated electromagnetic radiation being incident on the filter element. 
 
     
     
       15. The system according to  claim 1 , wherein at least one of:
 i) the frequency modulation device is a high frequency modulation device, or 
 ii) the frequency modulation device is configured to modulate with a frequency being higher than 500 Hz. 
 
     
     
       16. The system according to  claim 15 , wherein at least one of:
 i) the frequency modulation device is at least one of a photoelastic-modulator, a liquid crystal retarder, and a Pockels cell, or 
 ii) the frequency modulation device is configured to modulate with a frequency being higher than 1 kHz. 
 
     
     
       17. The system according to  claim 1 , wherein the masking device is configured to mask one or more areas of the detection device such, that the detection device is prevented from detecting incident intensity-modulated electromagnetic radiation in these one or more masked areas. 
     
     
       18. The system according to  claim 1 , wherein the detection device is configured to detect incident intensity-modulated electromagnetic radiation in synchronization with the detection modulation signal. 
     
     
       19. A method for measuring the optical activity of a sample, the method comprising the steps of:
 at least one of i) irradiating electromagnetic radiation onto a sample so as to excite the sample and modulating a frequency of the electromagnetic radiation being emitted from the excited sample with at least one frequency modulation signal of at least one frequency modulation device or ii) modulating a frequency of electromagnetic radiation being irradiated on to a sample with at least one frequency modulation signal of at least one frequency modulation device so as to excite the sample with frequency-modulated electromagnetic radiation, 
 synchronizing at least one detection modulation signal with the at least one frequency modulation signal using at least one synchronization device, 
 detecting electromagnetic radiation in synchronization with the at least one detection modulation signal using at least one detection device; and
 wherein the frequency modulation device is configured to separate components of incident electromagnetic radiation having two or more polarization states into components of electromagnetic radiation having one or more frequencies, and 
 wherein:
 i) the system further comprises at least one masking device, wherein the masking device is configured to mask one or more areas of the detection device such, that the detection device is prevented from detecting incident electromagnetic radiation in these one or more masked areas, wherein the synchronization device is in connection with the masking device, wherein the synchronization device is configured to send the detection modulation signal to the masking device, and wherein the masking device is configured to mask one or more areas of the detection device in synchronization with the detection modulation signal, or 
 ii) the synchronization device is in connection with the detection device, wherein the synchronization device is configured to send the detection modulation signal to the detection device, and wherein the detection device is configured to detect incident electromagnetic radiation in synchronization with the detection modulation signal. 
 
 
 
     
     
       20. The method according to  claim 19 , wherein the method measures the optical activity of a sample with a system comprising:
 at least one frequency modulation device; 
 at least one synchronization device; and 
 at least one detection device,
 wherein the at least one frequency modulation device is configured to modulate a frequency of incident electromagnetic radiation being at least one of i) emitted from a sample or ii) irradiated on to a sample with at least one frequency modulation signal, 
 wherein the at least one synchronization device is configured to receive the at least one frequency modulation signal, 
 wherein the at least one synchronization device is further configured to emit at least one detection modulation signal being synchronized with the at least one frequency modulation signal, and 
 
 wherein the system is configured such that the at least one detection device detects incident electromagnetic radiation in synchronization with the at least one detection modulation signal. 
 
     
     
       21. A method of producing a system for measuring the optical activity of a sample, the method comprising the steps of:
 Providing at least one frequency modulation device; 
 Providing at least one synchronization device; and 
 Providing at least one detection device,
 wherein the at least one frequency modulation device is configured to modulate a frequency of incident electromagnetic radiation being at least one of i) emitted from a sample or ii) irradiated on to a sample with at least one frequency modulation signal, 
 wherein the at least one synchronization device is configured to receive the at least one frequency modulation signal, 
 wherein the at least one synchronization device is further configured to emit at least one detection modulation signal being synchronized with the at least one frequency modulation signal, 
 wherein the system is configured such that the at least one detection device detects incident electromagnetic radiation in synchronization with the at least one detection modulation signal, 
 wherein the frequency modulation device is configured to separate components of incident electromagnetic radiation having two or more polarization states into components of electromagnetic radiation having one or more frequencies, and 
 wherein:
 i) the system further comprises at least one masking device, wherein the masking device is configured to mask one or more areas of the detection device such, that the detection device is prevented from detecting incident electromagnetic radiation in these one or more masked areas, wherein the synchronization device is in connection with the masking device, wherein the synchronization device is configured to send the detection modulation signal to the masking device, and wherein the masking device is configured to mask one or more areas of the detection device in synchronization with the detection modulation signal, or 
 ii) the synchronization device is in connection with the detection device, wherein the synchronization device is configured to send the detection modulation signal to the detection device, and wherein the detection device is configured to detect incident electromagnetic radiation in synchronization with the detection modulation signal.